"I can confirm that we have received some radar data, but we are not at liberty to release information from other countries. I appeal to all our partners to continue volunteering any and all information that could help us with the investigation and the search for MH370," Hussein, who is in charge of the operation said at a news briefing in Sepang, Malaysia, on the 12th day of the search for the missing plane.

Some sources involved in the investigation have voiced fears it could be drifting towards deadlock due to the reluctance of countries in the region to share militarily sensitive radar data or allow full access to their territory.

Police have searched the homes of the 53-year-old pilot Zaharie Ahmad Shah and co-pilot Fariq AbdulHamid, 27. Among the items taken were a flight simulator Zaharie had built in his home.

The methodical shutdown of the communications systems, together with the fact that the plane appeared to be following a planned course after turning back, have been interpreted as suggesting strongly that foul play, rather than some kind of technical failure, was behind the disappearance.

"Local and international expertise have been recruited to examine the pilot's flight simulator, some data has been deleted from the simulator and forensic work to retrieve this data is ongoing, I would like to take this opportunity to state that the passengers, the pilot and the crew remain innocent until proven otherwise," Hussein said.

An unprecedented search for the Boeing 777-200ER is under way involving 26 nations in two vast search "corridors": one arcing north overland from Laos towards the Caspian Sea, the other curving south across the Indian Ocean from west of Indonesia's Sumatra island to west of Australia.

Investigators probing the disappearance of the plane believe it most likely flew into the southern Indian Ocean, a source close to the investigation said on Wednesday.

"Some priority is given to that area, this morning I spoke to Admiral Locklear of PACOM (Pacific Command) in trying to identify equipment that would assist us in locating a possibility of a black box, if that is the focus and the French experts that I spoke to earlier this afternoon in looking onto the black box which took them two years in the Atlantic, the equipment that they used, we are now identifying the assets," he said.

Police officers on Wednesday were seen dragging out distraught family members of Chinese passengers from the news briefing room. Many of them have arrived in Sepang demanding answers on the location of the plane.

"I hope then I appeal to everybody that though we understand their concerns we are trying our very best and it is heart-wrenching, even for me," Hussein said.

Investigators piecing together patchy data from military radar and satellites believe that minutes later the plane turned sharply west, re-crossing the Malay Peninsula and following an established commercial route towards India.

After that, ephemeral pings picked up by one commercial satellite suggest the aircraft flew on for at least six hours. The data from the satellite placed the plane somewhere in one of the two corridors when the final signal was sent at 8:11 a.m.